Enhanced frame aggregation in a wireless network system

Abstract

Variable-length information-containing frames (e.g., MPDUs) are aggregated into a bitstream using frame delimiters to distinguish the frames. Aggregation and frame extraction techniques are provided that support recovery from bit errors that may be present in a frame delimiter. One class of techniques involves providing redundant length information in the frame delimiters, e.g., by using multiple copies of a length field or error correction codes usable to correct errors in the length field. The receiver can use the redundant information to detect and correct errors in the length field. Another receiver-side technique iteratively attempts to locate the end of the corresponding frame when a corrupt frame delimiter is detected. Conventional synchronization fields may be eliminated.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 676,038, filed Apr. 29, 2005, entitled “Improved Protocols for MPDU Aggregation in a Wireless Network System,” which disclosure is incorporated herein by reference for all purposes.BACKGROUND OF THE INVENTION[0002]The present invention relates in general to wireless networking systems and in particular to enhanced techniques for handling aggregated frames in a wireless networking system to improve throughput in the presence of bit errors.[0003]Wireless networks continue to grow in popularity, and various standards for wireless networks (e.g., the IEEE 802.11 family of standards, which now includes 802.11a, 802.11b, 802.11c, 802.11g) are available. Such standards facilitate network setup and interoperability of devices made by different manufacturers. As use of these networks increases, the demand for bandwidth increases, and protocols are continually evolving to m...

AI Technical Summary

Benefits of technology

[0015]Embodiments of the present invention provide techniques for extracting information-containing frames from a bitstream in which multiple frames are aggregated using frame delimiters to distinguish the frames. These techniques are capable of recovering from bit errors in a frame delimiter in at least some circumstances so that most or all of the bitstream remains usable. In some embodiments, when a frame delimiter does not provide reliable length information, an iterative attempt is made to identify the end of the corresponding frame so that this frame and any subsequent frames can be extracted. In other embodiments, the frame delimiters provide redundant copies of the length information for the frames; if one copy is corrupted, another copy may still be usable. In still other embodiments, error correction codes are provided in the frame delimiter, allowing the receiver to correct errors in the frame-length information. The use of any of these techniques may in some cases eliminate the need for conventional synchronization fields, saving some overhead.

Problems solved by technology

As overhead increases, throughput of data decreases, making the network less efficient.

Increasing the bit rate, however, can result in little or no increase in throughput.

This is because, to the extent that increasing the bit rate also increases the bit error rate, an increasing fraction of the available bandwidth must be used to retransmit corrupted information.

If, however, the SYNC field 116 is corrupted, the receiver would not detect the start of MPDU 102(2) and would not be able to recover the rest of the data.

Retransmission adds overhead, reducing the throughput of the network assuming that the available bandwidth remains fixed.

The SYNC field provides some protection, but as noted above, a corrupt SYNC field can cause the receiver to discard most or all of a PSDU.

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